Printing apparatus

ABSTRACT

A portable printing apparatus prints and color codes selected information on an elongated ribbon which is advanced between a printing roller carrying inkable characters and a pressure roller for holding the ribbon against the printing roller and printing the inkable characters on the ribbon as it advances. An ink roller with a self-contained supply of ink has an outer surface from which ink is releasable upon pressure contact with the ink roller to transfer ink to the inkable characters. In one form of the invention, several of the ink rollers are mounted on a rotatable turret. Each ink roller is adjustable independently toward and away from the printing roller so that ink of a plurality of colors may be selectively transferred to the inkable characters.

United States Patent Cunningham 1 1 Jan. 23, 1973 [541 PRINTING APPARATUS 1,496,331 6/1924 Wheelock ..101 212 3,227,080 1/1966 Hill ..l01/228 [751 invent l f Temple 3,253,542 5/1966 McDonough ..l0l/367 City, Calif. [73] Assignee: Royal Industries, Inc., Pasadena, Primary Examiner-Clyde l. Coughenour Calif. Att0rneyChristie, Parker & Hale [22] Filed: May 27, 1971 ABSTRACT Appl. No.: 147,375

Related U.S. Application Data Continuation-impart of Ser. No. 863,460, Oct 3, 1969, abandoned.

A portable printing apparatus prints and color codes selected information on an elongated ribbon which is advanced between a printing roller carrying inkable characters and a pressure roller for holding the ribbon against the printing roller and printing the inkable characters on the ribbon as it advances. An ink roller with a self-contained supply of ink has an outer surface from which ink is releasable upon pressure contact with the ink roller to transfer ink to the inkable characters. ln one form of the invention, several of the ink rollers are mounted on a rotatable turret. Each ink roller is adjustable independently toward and away [56] References Clted from the printing roller so that ink of a plurality of UNn-ED STATES PATENTS colors may be selectively transferred to the inkable characters. 108,785 11/1870 Hoe etal. ..10l/276 587,253 7/1897 Adler ..l0l/206 X 8 Claims, 5 Drawing Figures If 43 25 I77! l /2\ I I. I l l I I 15 I I L Q 659 g J ,182 1:11,:1: 53.2: ill 42142224 52; H (3,

PATENTEDJAH23I975 I I 3.712.215

sum 1 or 3 AL PAM A/U/MER/C CHARACTERS m INVENTOR. j EDSON WAYNE CL/N/V/A/G/IA/V/ /5,

PATENTEDJAN 23 I975 SHEET 2 [IF 3 PRINTING APPARATUS CROSS-REFERENCE TO RELATED APPLICATION This is a continuation-in-part of my copending application Ser. No. 863,460, filed Oct. 3, 1969 now abandoned.

BACKGROUND OF THE INVENTION This invention relates to a printing apparatus and more particularly to a portable printer capable of printing on tying ribbons and the like.

At the present time a number of articles are packaged in plastic bags and the like that are tied with tying material that can be twisted upon itself for the purposes of closing such bags. A very common article that is packaged and tied in this fashion is bread. One such tie strip is the subject of U.S. Pat. No. 3,409,948. Automatic machinery for tying such packages with such tie strips have also been developed and are in common use. The tie strips used in these automatic tying machines not only should be capable of being tied by twisting but also to have some legend such as pricing, days of the week and the like printed thereon at the time that the bags are being tied. At the present time, there is available printed apparatus for printing on such ties. The presently available printing apparatus may be used along with the automatictying machines so that the legend or information to be printed on the tie strips can be printed in accordance with the contents of the package being tied at the time of packaging thereby avoiding the necessity of preprinting the ties. The automatic tying machines for packaging bread have been used with prior art types of printing apparatus, coders and the like for placing the price of the bread or the day of the week that the bread was delivered to the grocers shelves or other similar information. In view of the limited amount of area available on such tie strips the day of week on which the bread is delivered along with the price cannot always be conveniently placed on such tie strips and some other mode of relating such information is necessary. As to bread packaging, for example, the date can be coded by color coding the price information a different color for each day of the week. A need, therefore, exists for printing apparatus that may be employed for printing on tie strips of the type that is the subject of U.S. Pat. No. 3,409,948 which allows the printing of information thereon and also allows for color coding other information such as the date of delivery of the packaged item.

SUMMARY OF THE INVENTION The present invention provides an improved inexpensive and portable printing apparatus that may readily be utilized with tying machines for printing and color coding selected information on the tie strips that are employed in such machines with a minimum of inconvenience to the user and may be employed with auto matic tying machines. One form of the present invention provides printing means for printing alpha-numeric characters on tie strips or ribbons in a'multiplicity of colors without changing ink rolls. For this purpose, the printing apparatus of the present invention comprises an inexpensive arrangement for printing in a multiplicity of different colored inks and for operating the printing apparatus for selectively transferring the various colored inks to the printing means proper without any special training on the part of the operator.

From a structural standpoint, the printing apparatus of the present invention is adapted to print upon a printable medium upon the transfer of ink to the printing means and the presentation of the printable medium to the printing means for transferring the ink under pressure to the printable medium. The printing apparatus comprises movable means mounted adjacent the printing means for selectively transferring ink of a plurality of colors to the printing means. Specifically, the printing apparatus is constructed and defined so that a tie strip or tying ribbon may be pulled through the printing apparatus between a series of rollers for causing the ink carrying printing means to transfer the necessary information to the ribbon during the travel through the printing apparatus. The ink carrying means preferably comprises an inking roller having a built-in supply of ink that is releasable under pressure. The inking roller is mounted for pressure contact with the printing roller to transfer ink to inkable characters on the printing roller. The inking roller preferably is releasably mounted adjacent the printing roller so it can be replaced with another inking roller having ink of a different color.

In one form of the invention, a plurality of the inking rollers, each having ink of a different'color, are ar-- ranged on a rotatable turret for rotation against the printing roller, the inking rollers being independently adjustable toward and away from the printing roller to selectively transfer ink of various colors to the printing roller. The inking rollers preferably are independently adjustable to effect the desired pressure for transferring the ink to the rollers. The rotatable turret is arranged to move in a linear fashion, up and down, to cause the various areas of the ink rollers to be exposed to the printing means for extending the life of the ink rollers. Stated differently, the ink rollers are not continuously being employed over the same area as in the prior art structures.

BRIEF DESCRIPTION OF THE DRAWINGS These and other featuresof the present invention may be more fully appreciated when considered in the light of the following specification and drawings, in which:

FIG. 1 is a top plan elevation view, with the cover removed, of the printing apparatus embodying the invention and illustrating a tie strip as it would move through the apparatus;

FIG. 2 is a cross-section elevation view taken along lines 2-2 of FIG. 1;

FIG. 3 is a cross-sectional elevation view of an ink roller taken along the lines 3-3 of FIG. 1;

FIG. 4 is a top plan elevation view, with the cover removed, of an alternative form of the printing apparatus; and

FIG. 5 is a cross-sectional elevation view taken along the lines 5--5 of FIG. 4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The printing apparatus of the present invention is mounted in an open ended enclosure '10 provided with a hinged cover 11. The printing means proper is illustrated in FIG. 1 in the top portion of the drawing and is identified by the reference numeral 12. The inking means for the printing apparatus is arranged below the printing means 12 and is identified by the general reference character 13. The printing means 12 is of more or less conventional construction and includes the printing roller 14 rotatably mounted opposite a rotatable pressure roller 15 to effect the printing operation. The printing roller 14, as is conventional, carries on its outer periphery a strip or a series of characters letters or numerals for effecting the printing upon inking. The ink carried by the printing roller 14 is transferred to the printable material upon presentation of the material between the rollers 14 and 15. The rollers 14 and 15 provide a pressure contact sufficient to effect the printing. Associated with the rollers 14 and 15 are a pair of rotatable pressure rollers identified as the rollers 16 and 17 and illustrated immediately to the right of the rollers 14 and 15 in FIG. 1. The rollers 16 and 17 are arranged in alignment for rolling contact with one another. The rollers 14 and 16 are mounted on a guide structure 17 that is pivotable about a pin 14 mounting the printing roller 14. In the same fashion, the rollers 15 and 17 are mounted on a guide structure 18 opposite the rollers 14 and 16, respectively, and which guide structure 18 is pivotable about the pin 17 mounting the roller 17. The guide structures 17 and 18 are mounted in abutting relationship with a channel 18 defined adjacent the abutting surface of the guide 17 for accepting and guiding the printable medium or tie strips through the printing apparatus.- Similar guide means having channel 20 defined therein and aligned with the channel 18 is arranged on the opposite side of the rollers 14 and 15 from the rollers 16 and 17 to accept and guide the printable medium as it is advanced past the printing roller 14.

A typical tie strip of the type which is printable and is the subject of U.S. Pat. No. 3,409,948 is illustrated in FIG. 1 extending throughout the printing apparatus as it would be advanced through the machine. The tie strip is identified by the reference character 21. The tying material 21 is advanced through the printing apparatus from the right-hand side to the left-hand side as illustrated in FIG. 1. The unprinted tie strip 21 is printed upon when it is advanced to the printing roller 14 and exits, printed, for the guide 20, as illustrated. The tie material 21 is advanced through the printing apparatus by being pulled therethrough either manually or automatically in response to the feeding of the tying material to the tying machine. It should be noted that the printing apparatus of the present invention is such that the pressure roller 16 is coupled to the printing roller 14 by means of a belt 22 or the like so that upon rotation of the roller 16 in response to the advancement of the tie material 21 past roller 16 the printing roller 14 is caused to rotate in unison therewith and causes the successive series of characters carried by the printing roller 14 to be imprinted on the tying material 21.

With the guides 17 and 18 arranged in abutting rela tionship as described hereinabove, it is not possible to move the tie material 21 through the machine to the printing roller 14 in view of the blocking action of the abutting rollers-l6 and 17. Accordingly, the guides 17" and 18 are each mounted in a pivotable fashion to allow the breakage of this contact to provide a sufficient gap to allow the tie material 21 to be advanced through the rollers 16 and 17. As previously indicated the guide 17 is pivotable about the pin 14 and is movable in a clockwise relationship as indicated by the positions of the roller 16 in dotted outline in FIG. 1. To maintain the normal position of the guide 17 with the guide 18 a compression spring 23 is secured adjacent the outer surface of the guide 17" by means of. a fastener 24. It should be noted that with this compression spring 23 that upon the release of the pivoting force, the spring 23 will urge the guide 17 back into its normal position. In the same fashion, the guide 18 may be pivoted about the point 17 so that the left-hand extremity of the guide 18 pivots in a clockwise direction as indicatedby the dotted outline of the roller 15. For this purpose the roller 15 has a pivot pin 15 extending upwardly from the surface to allow the operator to grasp it for readily providing the pivoting action. The guide 18 is also provided with a compression spring 25 mounted against the outer surface of the guide 18 and against the wall of the enclosure 10 for urging the guide 18 in its normal relationship with the guide 17.

The operation of the printing apparatus assuming that the printing roller 14 carries ink thereon is more or less conventional and can be briefly examined at that point. Assuming that the tie strip 21 is properly positioned within the printing apparatus, i.e., the guides 17 and 18 have been pivoted to allow the tie strip 21 to lay in the guide channels 18 and 20 defined by the guides 18 and 20, it should be noted that with the advancement of the tie material 21 the roller 16 is caused to rotate and thereby cause the printing roller 14 to rotate and thereby cause the characters carried by the roller to be sequentially imprinted on the strip 21.

At this point, it should be well to note that the printing structure 12 just described prints a tie strip in advancing from the right to the left as illustrated in FIG. 1 but that such a printing structure is reversible through the reversing of the guides 17-20. With the reversing of the guides 17-20 the printable medium may enter the printing apparatus from the left-handside and exit from the right-hand. For this purpose reversing mounting holes 28 and 29 are defined in the enclosure 10. It will be recognized that with the reversing of the guides 17-20 that the spring 23 will have to be relocated and thereversing hole 29 is to accept the fastener 24 for securing the spring 23 against the associated guide.

The inking means 13 comprises a plurality of ink rollers similar to the roller 30 mounted and carried on a rotatable turret plate 31 that allows the roller to be rotated into an ink transfer relationship with the printing roller 14. The rotatable plate 31 is mounted to the enclosure 10 by means of a helical screw 32. The helical screw 32 is fixed to the enclosure 10 by a flathead screw 10'". The turret plate 31 is provided with an integral hub 31 for securing theplate 31 to the screw 32. The arrangement of the indexing plate 31 and the helical screw 32 is such that by the rotation of the turret plate 31, it is caused to travel linearly up and down the helical screw in accordance with the direction of the rotation of the plate 31. The plate 31 is also adapted to be indexed a number of positions corresponding to the number of ink rollers carried thereon. For this purpose the plate 31 is provided with a series of indexing notches 31" arranged in the outer periphery of the plate in spacedapart relationship so that upon indexing the plate 31 a roller 30 will be arranged opposite the printing roller 14. For indexing purposes an indexing arm 33 mounted an upstanding indexing pin 33 is mounted to the enclosure 10. The indexing arm 33 is secured to the enclosure by means of a fastener 34 and arranged with a torsion spring 35 urging the arm 33 towards the indexing plate 31. The indexing arm 33 extends into the indexing notch 31" to secure the plate 31 in a selected position. The movement of the indexing arm 33 by grasping the indexing pin 33 to rotate the arm 33 counterclockwise will release the indexing plate 31 and thereby allow it to be rotated to a new position.

The indexing plate 31 is illustrated as carrying six ink rollers 30 mounted adjacent the outer periphery of the plate 31. Each of the rollers 30 are of a construction having a built-in ink supply and therefore no ink foun-' tain or the like is necessary with the apparatus of the present invention. The rollers 30 are preferably constructed of a porous plastic structure that is capable of holding a built-in supply of ink within its porous structure and such materials are commercially available from S. C. Johnson, Inc. of Racine, Wisconsin. Such solid inking materials have been sold by S. C. Johnson under the tradename Porelon for inking purposes. These Porelon rollers are constructed of a particular plastic material and have the ink supply built into them so that the ink cannot leak. The ink is transferred from such a Porelon inking roller to a printable means only under pressure. Each of the rollers 30 are mounted on the plate 31 in the identical fashion and therefore only one roller need be examined. The rollers 30 are mounted on a rotatable shaft 36 with an eccentric 37 arranged on the shaft adjacent the top surface of the plate 31. The shaft 36 is suitably journaled and secured to the bottom side of the indexing plate 3l','as best illustrated in FIG. 3, to allow the rollers to be independently adjustable. The outer end of the shaft 36 is provided with a knurled operating member 38 arranged on the opposite end of the shaft 36 from the eccentric 37. The eccentric 37 mounts a pin 37 extending from one end thereof for cooperating with the stop pins 39 and 40 mounted to the plate 31 and on opposite sides of the eccentric 37. The pins 39 and 40 are secured to a plate 31 to define the limits of travel of the roller 30 so that the roller may be positioned in engagement with the printing roller 14 with the correct amount of pressure for effecting the correct transfer of ink. In the position of the roller 30, illustrated in FIGS. 1 and 3, relative to the printing roller 14, it should be noted that the eccentric 37 is located as indicated in dotted outline in FIG. 1. When the shaft 36 is rotated by grasping the knurled member 38 the roller 30 is rotated away from the roller 14 and in its other extremity assumes a position as illustrated in dotted outline in FIG. 1.

From the above, it should be noted that for the purposes of coding information on the tie strip or a printable material that the ink rollers 30 may be provided with ink of different colors. For example, when it is necessary to identify the date of packaging for a loaf of bread the six rollers 30 may carry a different color ink so that upon printing the price of the bread on the tie strip 21, the color will show the baker and/or the grocer the day of the week that the bread was packaged or delivered. For example, if the price of bread is 37 cents, the bread appearing on the grocers shelf on Monday would have a price marked in red. The same bread purchased on Tuesday may have the price marked in blue and each day of the week the price would be printed in a different color.

The enclosure 10, as best appreciated from FIG. 2,-is a box-like construction with the open end closed by the cover member 11. When the printing apparatus of the present invention is employed with tying machines that are used in bakeries it has been found that foreign matter, such as bread crumbs, tend to lodge in the printing apparatus and hamper the operation. Accordingly, it has been practical to employ the cover 11 and for this purpose the cover 11 is hinged to one end of enclosure 10 by means of a suitable hinge 42. The opposite end of the enclosure is provided with a magnetic latch 43 for securing the cover 11 closed during operation of the printing apparatus.

FIGS. 4 and 5 show an alternative printing apparatus having an upwardly opening enclosure 10 which is smaller in volume than enclosure 10 shown in FIGS. 1 through 3. The guide means for advancing the tie strip 21 are substantially the same as that described above in FIGS. 1 through 3. Guide structures 17 and 18 extend substantially the entire width of the smaller enclosure 10, thereby eliminating the need for tie strip guide 20 shown in FIGS. 1 through 3. Compression spring 23, described above, is replaced in the present printing apparatus by a compression spring 44 connected between an outwardly projecting pin 45 on guide structure 17" and a pin 46 integral with the interior wall of enclosure 10. In use, spring 44 functions the same as spring 23 by urging guide structure 17 back to its normal position shown best in FIG. 4.

The printing apparatus shown in FIGS. 4 and 5 has inking means 48 for transferring ink to a plurality of inkable characters 14b (shown as a series of numerals in FIG. 5) on printing roller 14. The inking means includes a single ink roller 50 releasably carried on a rotatable vertical shaft 52. Ink roller 50 is identical in construction to the ink rollers 30 described above, roller 50 preferably being a porous plastic structure with an outer surface from which ink is releasable on pressure contact with the inkable characters on printing roller 14.

Ink roller 50 makes a releasable sliding fit on the upper end of shaft 52. The bottom of the ink roller rests against a laterally outwardly extending pin 54 rigidly secured to an intermediate portion of the shaft. The pin maintains the roller in a substantially fixed position on the shaft. A horizontal knurled operating knob 56 is threaded into the top of shaft 52 and tightened against the top of roller 50. In use, knob 56 functions the same as member 38 shown in FIGS. 1 through 3. The knob is grasped by the operator and turned to rotate shaft 52 toward and away from printing roller 14 in the manner described in detail below. Knob 56 also is removable from shaft 52 to permit ink roller 50 to be removed and replaced with another in'k roller. Thus, if the supply of ink in roller 50 becomes depleted, the roller may be quickly and easily replaced with a new ink roller. Alternatively, roller 50 can be substituted with another roller having ink of a different color when, for example, color coding for loaves of bread or the like is to be changed.

Shaft 52 is carried by an eccentric 58 rotatably mounted in a horizontal plate 60 which bridges a pair of opposed shoulders 62 formed integrally with the interior side walls of the enclosure. An intermediate portion 64 of the eccentric is suitably journaled in plate 60 so the eccentric rotates about a vertical axis through its center. The lower portion of the eccentric projects below the bottom surface of plate 60. A retainer ring 66 fitted in an annular slot at the bottom of the eccentric holds a pair of retainer rings 68 and a washer 70 in place against the bottom surface of the plate to thereby hold the eccentric securely in place in plate 60.

Shaft 52 extends through an opening in eccentric 58, with the vertical axis of the shaft being laterally offset from the axis of rotation of the eccentric. A laterally outwardly extending pin 72 is carried by the portion of eccentric 58 above plate 60. The pin 72 cooperates with a pair of spaced apart vertical stop pins 74 and 75 on plate 60 to stop rotational travel of the eccentric and thereby define the limits of travel of ink roller 50 in a manner identical to the stop pins 39 and 40 described above.

In use, knob 56 is rotated so that ink roller 50 may be positioned in engagement with the inkable characters on printing roller 14 with the correct amount of pressure for effecting the correct transfer of ink. Because of its eccentric mounting on eccentric 58, ink roller 50 may be rotated toward and away from the printing roller between the limits illustrated by the solid lines and phantom lines in FIGS. 4 and 5.

Shaft 52 is slidable vertically up and down in eccentric 58. As shown best in FIG. 4, a shoulder 76 at the outer end of pin 72 extends into a vertical slot 78 formed in the side of shaft 52 below ink roller 50. Shoulder 76 acts as a spline in preventing relative rotation of shaft 52 and eccentric 58. As the shaft slides upwardly in the eccentric, the bottom of slot 78 abuts against the bottom of shoulder 76 to limit further vertical travel of the shaft. When the shaft slides downwardly in the eccentric, stop pin 54 abuts against the top surface of the eccentric to limit further downward travel of the shaft. This arrangement permits ink roller 50 to travel linearly up and down on shaft 52. Thus, the vertical position of the ink roller relative to printing roller 14 may be adjusted vertically up and down so that various areas of the ink roller can be selectively exposed to pressure contact with the printing roller and thereby extend the life of the ink roller.

lclaim:

1. Printing apparatus comprising:

a. a rotatable printing roller carrying a plurality of inkable characters to be printed upon rotation against printable material;

b. a rotatable pressure roller rotatably mounted opposite the printing roller for holding the printable material thereagainst during printing;

0. an ink roller made of porous plastic material and having a self-contained supply of ink therewithin, the ink being releasable only upon pressure contact between the outer surface of the ink roller and the inkable characters;

d. means mounting the ink roller adjacent to the printing roller to provide pressure contact between the ink roller and the inkable characters, the mounting means including (i) means for selectively adjusting the pressure contact between the ink roller and the inkable characters including means for selectively moving the ink roller into and out of pressure contact with the inkable characters, (ii) means providing selective movement of the ink roller along its longitudinal axis to thereby selectively position different areas of the ink roller adjacent the printing roller to thereby extend the useful life of the roller, and (iii) a support on which the ink roller is mounted, and means for releasably securing the ink roller to the support, whereby self-contained ink rollers having different colors of ink may be selectively mounted on the support; and

e. guide means including a pair of pressure rollers rotatably mounted in rolling contact with one another on the printable material entry side of the printing roller and rotatable in response to the advancement of printable material therethrough, and means coupling one of the pressure rollers to the printing roller to cause the latter to rotate with the rotation of said one pressure roller.

2. Printing apparatus as defined in claim 1 wherein the support is mounted on an eccentric so the ink roller rotates toward and away from the printing roller.

3. Printing apparatus as defined in claim 1 including at least another ink roller having a self-contained supply of ink carried by the mounting means, said mounting means being adapted to provide selective movement of each ink roller into and out of pressure contact with the inkable characters.

4. Printing apparatus as defined in claim 3 wherein the mounting means includes individual means for mounting the ink rollers for rotation about an axis eccentric to the longitudinal axis of the ink roller.

5. Printing apparatus as defined in claim 1 in which an endless belt couples the pressure roller to the printing roller.

6. Printing apparatus as defined in claim 1 including a guide channel having an elongated groove through which the printable material is advanced during guided movement thereof,'and in which said pair of pressure rollers project into the groove'to receive the printable material therebetween, and in which a third pressure roller and the printing roller project into the groove at a location spaced longitudinally from said pair of pressure rollers and are mounted in rolling contact with one another to receive the printable material therebetween during its advancement through the groove.

7. Printing apparatus comprising:

a. a rotatable printing roller carrying a plurality of inkable characters to be printed upon rotation against printable material;

b. a rotatable pressure roller rotatably mounted opposite the printing roller for holding the printable material thereagainst during printing;

c. a plurality of ink rollers each having a self-contained supply of ink on an outer surface from which the ink is releasable upon pressure contact between the ink roller and the inkable characters; and

d. mounting means for the ink rollers adapted to provide pressure contact between each ink roller and the inkable characters, the mounting means in-.

cluding v(i) a support, (ii) an indexible turret plate mounting a plurality of said ink rollers thereon,

9 M (iii) helical screw means rotatably mounting the rotation of the turret plate, and (v) means for turret plate to the support and causing the plate to selectively adjusting the pressure contact between travel up and down on the helical screw means to each ink roller and the inkable characters. thereby position different areas of the ink rollers Printing appar s a d fi ed in claim 7 including dj t h imi ll (i means f i d means for enclosing said apparatus including removaing the turret plate and holding it in a preselected ble cover means for eXPOSmg the apparatus to the position whereby a different ink roller is moved operatoradjacent the printing roller with each movement of 

1. Printing apparatus comprising: a. a rotatable printing roller carrying a plurality of inkable characters to be printed upon rotation against printable material; b. a rotatable pressure roller rotatably mounted opposite the printing roller for holding the printable material thereagainst during printing; c. an ink roller made of porous plastic material and having a self-contained supply of ink therewithin, the ink being releasable only upon pressure contact between the outer surface of the ink roller and the inkable characters; d. means mounting the ink roller adjacent to the printing roller to provide pressure contact between the ink roller and the inkable characters, the mounting means including (i) means for selectively adjusting the pressure contact between the ink roller and the inkable characters including means for selectively moving the ink roller into and out of pressure contact with the inkable characters, (ii) means providing selective movement of the ink roller along its longitudinal axis to thereby selectively position different areas of the ink roller adjacent the printing roller to thereby extend the useful life of the roller, and (iii) a support on which the ink roller is mounted, and means for releasably securing the ink roller to the support, whereby self-contained ink rollers having different colors of ink may be selectively mounted on the support; and e. guide means including a pair of pressure rollers rotatably mounted in rolling contact with one another on the printable material entry side of the printing roller and rotatable in response to the advancement of printable material therethrough, and means coupling one of the pressure rollers to the printing roller to cause the latter to rotate with the rotation of said one pressure roller.
 2. Printing apparatus as defined in claim 1 wherein the support is mounted on an eccentric so the ink roller rotates toward and away from the printing roller.
 3. Printing apparatus as defined in claim 1 including at least another ink roller having a self-contained supply of ink carried by the mounting means, said mounting means being adapted to provide selective movement of each ink roller into and out of pressure contact with the inkable characters.
 4. Printing apparatus as defined in claim 3 wherein the mounting means includes individual means for mounting the ink rollers for rotation about an axis eccentric to the longitudinal axis of the ink roller.
 5. Printing apparatus as defined in claim 1 in which an endless belt couples the pressure roller to the printing roller.
 6. Printing apparatus as defined in claim 1 including a guide channel having an elongated groove through which the printable material is advanced during guided movement thereof, and in which said pair of pressure rollers project into the groove to receive the printable material therebetween, and in which a third pressure roller and the printing roller project into the groove at a location spaced longitudinally from said pair of pressure rollers and are mounted in rolling contact with one another to receive the printable material therebetween during its advancement through the groove.
 7. Printing apparatus comprising: a. a rotatable printiNg roller carrying a plurality of inkable characters to be printed upon rotation against printable material; b. a rotatable pressure roller rotatably mounted opposite the printing roller for holding the printable material thereagainst during printing; c. a plurality of ink rollers each having a self-contained supply of ink on an outer surface from which the ink is releasable upon pressure contact between the ink roller and the inkable characters; and d. mounting means for the ink rollers adapted to provide pressure contact between each ink roller and the inkable characters, the mounting means including (i) a support, (ii) an indexible turret plate mounting a plurality of said ink rollers thereon, (iii) helical screw means rotatably mounting the turret plate to the support and causing the plate to travel up and down on the helical screw means to thereby position different areas of the ink rollers adjacent the printing roller, (iv) means for indexing the turret plate and holding it in a preselected position whereby a different ink roller is moved adjacent the printing roller with each movement of rotation of the turret plate, and (v) means for selectively adjusting the pressure contact between each ink roller and the inkable characters.
 8. Printing apparatus as defined in claim 7 including means for enclosing said apparatus including removable cover means for exposing the apparatus to the operator. 